2010 Prius 2 here, I recently treated myself to a new jvc head unit and a set of new Rockford fasgate door speakers and memphis audio dash corner speakers. In the front doors they are component speakers, so there’s a sub and a tweeter in there, and the dash speakers are just full range spekers. The back doors are just full range fasgate speakers. When I crank the volume, as I do frequently, the sound quality takes a nosedive. I assume the way to fix this is with a new amplifier, but I have no idea what kind I need. How many channels, how many watts, and what is going to get me the most out of my fancy new speakers?? Any helpgeezgreatly appreciated!
The cheapest fix would probably be going back over the speaker installation and adding a bit of glue and insulation here and there to reduce rattles and sympathetic vibration. Your speakers are probably making great sound, but they may also be causing a part of the door to vibrate almost as loud and with far less control, which muddies up the sound badly. The loudest fix would be adding a 4-channel amplifier, something north of 50W per channel. You would use one channel per door. The front door speaker would be wired in parallel with the same-side tweeter. (You are probably already wired like that for the JVC) The bump-est fix would be adding a powered subwoofer. That way the door speakers don't have to work nearly as hard to produce bass sounds- they aren't very good at it anyway. A sub has the physical size to produce those sounds easily, and with a built-in amp it's relatively easy to install. This removes much of the workload from the JVC built-in amps, so they will sound much better driving the new RFs.
I think it is even more likely that the distortion is from having speakers of the wrong impedance for the amp in the radio. I suggest a visit to a respected "custom car audio" shop in the area.